Thresholds for the perception of 6 primary odorants were tested in a sample of 153 unrelated healthy individuals including 101 males and 52 females. Using some special precautions and directions for preparing aqueous solutions of primary odorants, screening for specific anosmia was found to be a practicable method with reliable results. The observed perception thresholds showed a bimodal distribution. Individuals with higher values probably are specific anosmics. Relatively lower frequencies of anosmia observed in this sample, as compared to reported values in Caucasians of the USA, are probably due to genetic differences. The pheromone character of some odorants and their possible genetic relevance is discussed.